"So asks gwern in a spectacular display of hindsight. The short answer about why it took so long is that the bit gold/Bitcoin ideas were nowhere remotely close to being as obvious gwern suggests. They required a very substantial amount of unconventional thought, not just about the security technologies gwern lists (and I'm afraid the list misses one of the biggest ones, Byzantine-resilient peer-to-peer replication), but about how to choose and put together these protocols and why. Bitcoin is not a list of cryptographic features, it's a very complex system of interacting mathematics and protocols in pursuit of what was a very unpopular goal." ‎· silpol